1. Field of the Invention
The present invention relates to a magnetic shielding sheet, its manufacturing methods and uses. The sheet can be freely wound on electronic devices such as cables.
2. Description of the Related Art
Nowadays, a remarkable progress in intelligence and communication techniques and the use of computers, organization of network systems (to connect each computer with communication circuits) has been developing in a wide range of industrial fields. In the manufacturing field, many types of control devices, measuring equipment, and sensors are used accompanied by factory automatization through computers. But a problem arises due to leakage of magnetism into the surroundings from cables (such as those which supply electric current or which are used for communication), motors, magnetrons, and magnetic driving instruments. Leakage also occurs due to crosstalk between adjacent wiring boards, malfunctions in the electronic circuits in a computer. In order to prevent such a leakage of magnetism or to stop the effect of the leakage of magnetism, use of so-called magnetic shielding materials has become a common practice.
For such magnetic shielding materials, rolled plates made of permalloy or shaped members made by forging and pressing are used. These plates and shaped members are manufactured from plate materials by cutting, bending, and welding and they are used to shield rooms and spaces (where computers and other devices which contain electronic circuits are installed) from the effect of magnetism. To shield an electronic device having a particular size and shape, a number of receptacle forming members similar in form must be made by forging, pressing, and assembling.
But permalloy is expensive and requires extensive processing as described above and the shield materials from permalloy are also expensive. In addition the processing causes localized distortion which results in reduction of the magnetic shield characteristics. Moreover, the increase in weight and space for installation restricts the extent of application. It has been also extremely difficult to wrap or paste the shield material in the form of a plate on surfaces of various cables, in and outside electronic devices, or inside a computer room because of low flexibility in shape. Particularly, it has been almost impossible to put shields after laying cable, after assembling electronic device, or after completion of computer room construction.
An object of the present invention is to solve the conventional technical disadvantages described above and provide magnetic shielding sheets, manufacturing methods, and cables which include the shielding sheet. It is also an object of the invention to provide magnetic shielding sheets which are able to freely and easily cover on individual object, with no increase in weight and space, with a low manufacturing cost, regardless of the source of the occurrence, shape and size of the object, position of its installation, conditions, and the surrounding spatial situation.